Conventionally, when detecting a human body using motion information, determination on the size of an object detection region has been used for removing noise. However, an object with a motion to be detected may not only be a human body. A standard detection region unique to a human body (hereafter simply referred to as a standard human region) is prepared, and the size of an object detection region of an object with motion detected is compared with the standard human region so as to determine whether or not the object with the motion detected is a human body. More specifically, when the size of the object detection region is close to the size of the standard human region, the object detection region is determined as a human detection region.
In general, the size information of the standard human region is stored in a memory as a table in advance. The size information of the standard human region includes only one row of the image in the horizontal direction stored in the memory as illustrated in FIG. 1, and the size information of the other rows is substituted by the information stored.
In an omnidirectional image captured by an omnidirectional camera, in order to detect a human body by determining the size using the standard human region as described above, it is necessary to take change in the size of a captured image of a human body according to a position on an omnidirectional image into consideration. More specifically, as illustrated in FIG. 2, even when attempting to use the standard human region size information for one row in the horizontal direction, the size of the image changes into a radial direction from the image capturing center in an omnidirectional image. Accordingly, it is difficult to adopt the change using the size information for one row. In an omnidirectional image, even if the pixels are in the same row, the size of the pixels changes significantly if the pixels are in different columns.
Taking these problems into consideration, PTL1 discloses a technique for changing the size of the standard human region according to a distance from the center of the omnidirectional image.
In addition, conventionally, a human body and its shadow are separated using a detection region. The method utilizes the difference between the human detection region and a shadow detection region in aspect ratio, that is, while the human region is longer in the vertical direction in an aspect ratio, the shadow detection region is longer in the horizontal direction.